What’s the difference between a 1959 2nd De la Rue set & the 1963 Bradbury castles set?

They both share the same watermark but are different shades. The De La Rue colours are softer & are printed on a thicker and creamier paper. The Bradbury printings are printed on a thinner white paper and the colours are deeper with more detail in the diadem.

An easy way to tell the difference

When held near a heat source i.e. spotlight, the 1959 De La Rue stamps curls horizontally that is from the top to the bottom. The 1963 Bradbury printings curl vertically that is left to right.